Catalytic motor fuel production



July 14, 1942. R. -F. MARscHNER OA'LLYMO MOTOR FUEL PRODUCTION 'Filedoct. 19, 19:59

Patented July 14, 1942y UNITED 'STATE CTALYTIC MOTOR FUEL PBOIUCTIONRobert F. Marschner, Chicago, Ill., asslgnor to Standard Oil Company,Chicago, Ill., a corporation of Indiana vApplication October 19, 1939,Serial hlm-300,229

1|)v Claims. (Cl. 196-v-49) This invention relates to the production ofhigh quality motor fuel by catalytic processes and it pertains moreparticularly to the prepa-ration of aviation gasoline in an improvedsystem employing catalytic dehydro-aromatization, catalytic cracking andcatalytic hydrogenation.

Motor fuelproduced by catalytic cracking may be objectionable foraviation purposes because of itsy higholenic content and its consequenthigh acid heat. The acid heat test is a common method for determiningthe unsaturated content of gasoline and is described, for example involume IV of Science of Petroleum, page 2430 According to this test theacid heat number is expressed as th'e number of degrees F. rise intemperature, following the addition of 30 cc. of 66 B. sulfuric acid to150 cc. of fuel to be tested .in a Dewar ask. Themixture is thoroughlyagitated and the temperature e during a three minute Aperiod followingthe ad ition of the acid a low acid heat.

Benzol is objectionable as a motor fuel in many instances because of itslow total heat content. However, benzol and alkyl substituted benzolshave excellent antiknock properties. An object of the invention is toprovide a motor fuel which 'contains substantial quantities ofaromatics, which is characterized by a high octane number and whichsimultaneously meets rigid specifications with regard to total heatcontent.

Afurther object of the invention .is to provide an improved aviationgasoline which'will meet rigid volatility specifications and in whichthe various componentsof different boiling range areV chemicallyconstituted to obtain maximum overall antiknock propertiesy and toinsure the most elcient' engine performance. A further object is toprovide a motor fuel with good lead response, i. e., one in whichtheaddition of small amounts of lead tetraethyl will produce 4relativelylarge' increases in octane number.

A further object is to provide a new combina# tion of catalystconversion systems with means for producing the hydrogen in one part ofthe system and utilizing said hydrogen in another part of the system. Afurther object is to provide an improved method for treating thecomponents of a petroleum oil or oil fraction whereby maximum yields ofhigh quality gasoline are obtained in each step with a minimumdegradation to gas and coke.

Cil

tively and efliciently to utilize catalytic .cracking in a combinationsystem involving dehydroaromatization and hydrogenation. A furtherobject is to provide an improved process wherein the hydrogenation stepis applied only to a particular and relatively small fraction of thematerials which have previously undergone catalytic conversion steps.Other objects will be apparent as the detailed description of theinvention proceeds.

'Ihis invention is based on the discovery that certain naphtha, gas oilor heavy oil fractions fis expressed as the acid heat. `An object of myinvention is to catalytically produce a high knock -catalyticallyproduced gasoline prior to hydrorating motor fuel l'which will becharacterized by require different conversion conditions than do otherfractions and that heavy fractions produced by dehydro-aromatization areparticularly amenable to catalytic cracking. I have found that it isunnecessary to hydrogenate the entire gasoline fraction from catalyticcracking in order to obtain a finished gasoline of desired low acidheatk and high lead response and an important feature of my invention isthe fractionation of genation so that only the small fraction issubjected to hydrogenation. Furthermore, only partial hydrogenation ofthis fraction is necessary and even desirable. I have found that thedesired A further object of the invention is more effecchemicalconstitution of the individual hydrocarbons which make up nishedgasoline is best obtained if: (a) the C4 and C5 fractions are kept outof the charging stock to the dehydro-aromatization unit; (b) the naphthafractions are subjected to dehydro-aromatization; (c) the heavierfractions together with heavy products from dehydro-aromatization aresubjected to catalytic cracking; and (d) the light catalyticallyjcrackednaphtha (which may include light aromatized naphtha) is partiallyhydrogenated without hydrogenating the hea y fractions. Referring morespecifically to the partial hydrogenation, I have found thatcatalytically cracked gasoline contains two types of oleilns: theunsubstituted ole- -ns and the branched chain, substituted or isoolens.I have found that the unsubstituted oleilns are hydrogenated much moreeasily than the substituted olefns. Thus the two hexenes cm-Ld-cmcm andblending octane number, but the-second hydrogenates much more easilythan the first.

Furthermore, the lighter parains such as isoand n-pentanes showexceptionally high lead response, making hydrogenation of these cutsdesirable. On the other hand hydrogenation of the heavy cuts isundesirable, even if carried out partially, since the less branchedparafhns, although showing a high lead response,`have extremely lowoctane numbers, causing an excessive fall in O. N. upon hydrogenation.

Partial hydrogenation of the lighter fraction of catalytically crackedgasoline, when effected to the extent of 20% to 90%, preferably about6075%, selectively leaves unhydrogenated the substituted olefins (towhich much of the clear octane number of the gasoline may be attributed)and give a product of low acid heat which will have an increased leadtetraethyl response.

Complete hydrogenation of a cut boiling at ISO-160 lowers the O. N. from81 to 72, whereas hydrogenation of 225250 cut lowers the O. N. from 80to 62. This O. N. lowering is even greater in such fractions as the350-400 cut.

The partial hydrogenation may be effected with the impure hydrogenproduced in the system itself and the utilization of this hydrogen inthe finished motor fuel results in increased gasoline yield. Not onlymay impure hydrogen be used for securing this partial hydrogenation, butthe catalysts employed may likewise be of only mod-- erate activity.They are therefore less expensive and are longer-lived than catalystsordinarily employed for absolutely complete hydrogenation of olefins toparafiins.

In practicing my process I fractionate the charging stock into a C5 andlighter fraction, a naphtha fraction and a heavy fraction. The C4 and Cshydrocarbons may -be yblended directly with finished gasoline, anyexcess being withdrawn from the system. The naphtha is catalyticallydehydro-aromatized to increase its knock rating and to supply hydrogen.The heavy fraction is c'atalytically cracked and fractionated. Lightvnaphtha produced by catalytic cracking (which may have an end point ofabout 150 to 250 F. and which may include light naphtha produced bydehydru-aromatization) is then partially hydrogenated with the hydrogenproduced in the dehydro-aromatization step. The heavy cracked naphtha,which may have an initial boiling point of about 150 to 250 F. and anend point of at least 350 to 400 I` is blended with the finishedgasoline without hydrogenation. By means of this integrated catalyticsystem I obtain maximum yields of high octane number gasoline which whenproperly fractionated and blended not only meets motor fuel requirewentsbut which meets the rigorous requirements of aviation gaso- Theinvention will be more clearly .understood from the following detaileddescription read in conjunction with the accompanying drawing whichforms a part of this specification and which is a simplified schematicflow diagram of my improved conversion system.

My invention is not limited to any particular feed; it may carbonaceousmaterials, by the catalytic conversion of carbon monoxide and hydrogenor by any other known method. Preferably the original charge isstraight-run or parainic hydrocarbon of wide boiling range and arelatively low octane number. In 'the preferred embodiment of the in-'be either straight-run or crackedV or it 4may be produced by thehydrogenation ofl vention I will describe the conversion of straightruncharge obtained from East Texas crude.

The catalyst employed for the naphtha reforming or dehydro-aromatizationstep is preferably an oxide of a VI group metal mounted on activealumina or activated alumina (a form of alumina obtained as a scale in'aluminum ore purification) or alumina gel. About 2 to 10% of molybdenumoxide on alumina or about 8 to 40% of chromium oxide on alumina havebeen found to give excellent results. The minor ingredient of thecatalyst is preferably an oxide or sulde of'molybdenum, chromium,tungsten or uranium or any mixture thereof mounted on bauxite,precipitated alumina, activated alumina" or any other suitable catalystsupport. Magnesium, aluminum or zinc chromites, molybdenites, etc. maybe employed. Vanadium and cerium oxides have been found to be eiectivefor this conversion. Oxides of copper, nickel, manganese, etc. may beincluded to' facilitate regeneration or to supplement or promotecatalyst activity. It should be understood, however, that the present4invention is not limited to any particular catalyst but is `applicableto the use of any dehydroaromatization catalyst known to the art.

The catalyst may be made by impregnating "activated alumina or othersupport with molybdic acid, ammonium molybdate or any other cata.- lystcompound decomposable by heat. Also the aluminum and molybdenum oxidesmay be coprecipitated as a gel or the separate oxides may be mixedtogether as a paste, dried, extruded under pressure or pelleted andheated to a temperature of about 1000 to 1200 F. Since the preparationof the catalyst forms no part of the present invention it will not bedescribed in further detail. t

For the catalytic' cracking step the catalyst is preferably anlactivated hydrosilicate of alumina or an active silica gel impregnatedwith a metal oxide, although it should be understood that crackingcatalysts of any known type may be used. So-called natural catalysts maybe made by treating fullers earthjor other natural clays with acid orwith aqueous solutions of chlorides or sulfates of magnesium, aluminum,manganese, etc. the ,treated catalyst then being washed, dried andpelleted. An acid-treated clay of the type commonly marketed asSuper-Filtrol has been found to be an excellent catalyst for crackingand is an example of the so-called "activated clay commonly used in thedecolorizing of lubricating oils, which activated clays are also goodcracking catalysts.

Synthetic cracking catalysts may be prepared by depositing on silica geloxides of such metals as aluminum, cerium, beryllium, thorium, zir-lconium, cadmium, copper, boron, titanium, manganese, magnesium, etc.Natural or artificial zeolites may be used as cracking catalysts whenthe alkali metals therein have been replaced by oxides of the metalshereinabove listed, particularly aluminum, copper, cadmium, manganese,magnesium, etc. 'Ihe catalyst may be used in granular or pelleted formand it may for instance be made into a thick slurry or paste, molded,pelleted or extruded by conventional means, dried at about 300 to 400 F.and nally heated to about 800 to 1200 F. or higher. The preparation ofthe cracking catalyst forms no part of the present invention and it willnot -be described in further detail.

Cil

rality of beds in vertical towers or chambers.

The moving catalyst may be charged to the top of a tower or tube eithercontinuously or intermittently, the spent catalyst being withdrawn fromthe base of the tube at substantially the same rate; in this case thereaction takes place continuously and under substantially constantconditions of temperature and pressure, the regeneration being eifectedoutside of the conversion zone. The powdered catalyst may be fed into arapidly moving stream of vaporized naphtha and hydrogen, separatedtherefrom after reaction is completed and separately regenerated byoxygen while suspended in flue gas. Any of these specific catalystreactors or their equivalents may be used in practicing the invention,but they will not be described in further detail.

Referring specifically to Figure 1, a crude East Texas petroleum ispassed from a heater or pipe still (not shown) through line I tofractionator I I` from which a butane-pentane fraction is withdrawnoverhead through line I2, a naphtha fraction is Withdrawn through lineI3 and 'a heavy fraction such as gas oil is withdrawn through line I4lubricating oils or tarry fractions being withdrawn through line I5.

The naphtha fraction may be supplemented by other naphthas from outsidesources introduced through line I6. Generally speaking, the boilingrange of this fraction will be in the general range of from about 150 to350 F. and it will contain predominantly hydrocarbons ranging from about6 to 12 or 14 carbon atoms per molecule. This naphtha fraction is passedby pump I1 through coils I8 of `furnace I9 and thence through transferline to catalyst chamber 2 I.

Hydrogen from line 22 may be passed by compressor 22a through line 23for admixture with charging stock in line I3 or it may be passed throughseparate coil 24 in furnace I9 and then introduced into transfer line 20or directly into catalyst chamber 2l.

The reaction in the catalyst chamber is preferably effected at a spacevelocity of about 0.04 to 10, preferably about 0.2 to 2-fvolurnes ofliquid naphtha per volume of catalyst space per hour at a temperature ofabout 875 to 1075 F., preferably about 950 450 pounds per square inch,preferably about 200 pounds per square inch, and in the presence ofabout .4 to 8 mols of hydrogen to 1 mol of-naphtha, preferably Iabout 3mols of hydrogen per mol of naphtha. 1

Reaction products and vapors leave reaction chamber 2I through line 25,are passed through heat exchanger 25 and cooler 21 and are thenintroduced into hydrogen separator 28 which is preferably maintained atsubstantially reaction pressure but at a temperature of about to 105 F.Separated hydrogen is withdrawn through line 29 (any excess or undulylow grade hydrogen being vented through line 30) and boiling range(so-called polymers) are withdrawn through line 31 and removed from thesystem through line 38 or preferably introduced through line 39,together with gas oil from line I4, into the coils 40 of pipe still 4I.Outside gas oil may be introduced into line I4 thru line Ila when crudescontaining high proportions of.

naphtha are charged to -fractionator II. The charging stock is heated incoils 40 to a temperature of about 875 to 925 F. under 'a pressure ofabout atmospheric to 50 pounds per square inch and is then introduced bytransfer line 42 to catalytic cracking chamber 43. Space velocity in thecracking' chamber is preferably about 0.5 to 2 volumes of liquid feedper volume of catalyst space per hour, and the average crackingtemperature is preferably about 850 to 950 F.

Products from the catalytic cracking step are withdrawn through line 44and introduced into fractionating column 45 which is provided withsuitable reflux and reboiler means. Hydrogen and hydrocarbon gases aretaken overhead through line 46. A light cracked naphtha fraction with anend point preferably within the range of 150 to 250 F. is withdrawnthrough line 41. Heavy cracked naphtha .is withdrawn through 48 andgas-oil and heavier fractions are removed from the base `of the columnthrough line 49; these heavier fraction may either be removed from thesystem through line 5i] or returned by pump 5I and line 52 to line I4for further cracking. It should be understood, of course, that anynumber of side streams may be taken from this fractionator and thatsuitable side stream strippers or other expedients may be employedforobtaining the desired boiling range, flash point, end point,volatility, etc. of each fraction. Instead of employing only a singlegasoline F., at a pressure of about 50 to passed by pump 3| to hydrogenstorage 32.

Liquid from separator 28 is withdrawn through line 33, heated inexchanger 26 and introduced into fractionator 34 fro-m which gases aretaken overhead through line 35 and aromatic gasoline is withdrawn as aside stream through line 36. Products boiling above the gasoline ormotor fuel storage tank l may employ a number of tanks, particularlywhen motor fuel and aviation fuel of different grades are desired.

An important feature of the invention is the segregation of the lightcracked naphtha for subsequent partial hydrogenation. As hereinabovepointed out, the partial hydrogenation of this particular fraction doesnot materially lower its octane number` while lit markedly lowers itsacid heat and markedly improves its response to lead tetraethyl. Thislight cracked naphtha of about to 250c F. end point, withdrawn throughline 41 is -passed through coils 53 of furnace 54 and then introducedthrough transfer line 55 to hydrogenation reactor 56. Hydrogen may beintroduced from storage tank 32 and line 51 either through line 58 withincoming charging stock or through separating heating coil 59 whichdischarges into transfer line 55` or into the hydrogenation chamber 5G.Pump 60 and compressor 5I are provided in lines 41 and 51, respectively,for maintaining the necessary hydrogenation pressure which may vary from50 pounds or lower to upwards of 3,000 pounds, depending upon thecatalyst temperatures, space velocities,

etc. employed in the hydrogenation reactor.

The hydrogenation catalyst may be of any type known to the art. Oxidesor suliides of VI group metals such as molybdenum, tungsten,-

metals supported 'on pumice, silica or preformed porcelain may beemployed. In the case of the VI group oxides or sulfides thehydrogenation conditions may be about the same as those used and otheroperating conditions will be controlled to bring about only partialhydrogenation, i. e. a saturation of about 20% to 90% or preferablyabout 60 to 75% of the oleflns in the cracked light naphtha. Thepressure for such hydrogenation Amay be from about 200 to about 3000pounds per square inch. The space velocity may be higher than that usedin dehydrogenation, for instance about 1 to 5 volumes of charging stockper volume of catalyst space per hour. The temperature may be somewhatlower than that used for dehydrogenation, i. e. of the order of 550 to850 F.

When catalysts such as nickel are employed dehydrogenation may beeffected at lower pressures, ranging from atmospheric to 50 pounds. Thetemperatures may be from about 350 to 450 F. and space velocities may beof the order of 8 or 10 volumes of liquid charged per volume of catalystspace per hour. The hydrogenation step per se is, of course, well knownin the art and I modify this Well-known process by employingsufficiently higher space velocity or sufficiently lower temperature orpressure to obtain only partial instead of complete saturation of theolefins in the light cracked naphtha.

Products from the hydrogenation reactor 56 are passed by line 62 throughcooler 63 to hydrogen separator 64. If the hydrogen is sufiiciently purefor reuse it may be returned by pump 65 and line 66 to storage tank 32.The hydrogenated products are Withdrawn from the base of the separatorthrough line 61 and are further fractionated if such fractionation isnecessary before being passed to the proper gasoline storage tank.

If the gases in line 46 do not contain appreciableamounts of hydrogenthey may be passed directly to line l2. Butanes and pentanes from `linesI'2, 35 and 46 may then be passed through cooler 68 to separator,stabilizer or depropanizer tower 68, from which propane and lightergases are taken overhead through line 10 and pentane, together with somebutanes are withdrawn as a liquid through line 1|. Excess butanes andpentanes may be vented through line 1| a.

If the gases in line 46 contain sufficient hydrogen for recovery suchgases may be compressed by compressor 12 land introducedv through line13 and cooler l14 to hydrogen separator 15, the hydrogen passing by line16 to line 66. vLiquid from separatoris preferably introduced Iby line11 to tower 69. When the gases from separator 64 for dehydrogenation,except that space velocity contain substantial quantities ofhydrocarbons v such gases may be passed by line 18 to line 13 forseparately recovering hydrogen and hydrocarbons as hereinabovedescribed.

'I'he final gasoline is composed of two or more of the followingproducts: (a) aliphatic Ce hydrocarbons (containing also C4 and Cchydrocarbons) from line 1|; (b) aromatic hydr-ocarbons from line 36; (c)partially saturated branched chain aliphatic light naphtha from line 61;and (d) heavy cracked naphtha from line 48. Various blends of gasolinemay be produced from these products, either for ordinary motor fuel orfor aviation fuel. Such fuels will be characterized .'by a low acidheat, a very high octane number, a relatively high total heat contentand a good 'lead tetraethyl response. The overall chemical compositionsof such fuels will differ from any heretofore produced 'because theheavy fraction thereof will be more highly olenic than the lightfractions and beca-use of the aromatic and branched chain structureswhichresult from the various conversion steps.

Instead of employing separate fractionating columns 34 and 45, ashereinabove described, I may eliminate fractionator 34 with itsassociated lines 35, 3B, 31, etc. and pass the products from line 33through line 19 to line 44 for fractionation in column 45. This effectsconsiderable savings in investment costs. Furthermore, by fractionatingmaterials from line 33 and line 44 in a common fractionating column Imayl hydrogenate the undesirable cracked olens which are present in thelight aromatic gasoline fractions along with the olens present in thelight cracked gasoline fraction, thereby increasing the overall heatcontent and markedlyl improving the lead response of the finishedgasoline. In this modification the heavier-than-gasoline aromaticproducts are withdrawn through line 49 and they may either be returnedby line y52, line I4 as hereinabove Aciescribed, or they may be returnedby lines 52 and to crude fractionator I l.

While I have described in detail a preferred embodiment of my inventionit should be understood that I do not limit myself to such details sincemany alternatives and modifications Will be apparent to those skilled lnthe art.

I claim:

1. The method of producing high quality aviation fuel from petroleumhydrocarbons containing fractions of the naphtha .boiling range andfractions boiling above the naphtha boiling range, which methodcomprises separating hydrocarbons of the naphtha boiling range fromheavier hydrocarbons, dehydro-aromatizing the hydrocarbons of thenaphtha boiling range to produce an aromatic gas-oline fraction and aheavy fraction, catalytically cracking the combined heavierthan-naphthafraction and the heavy fraction from the dehydro-aromatization step,separating the catalytically cracked products into a light crackedgasoline and a heavy cracked gasoline fraction, respectively, partiallyhydrogenating the light cracked gasoline fraction and blending thearomatic gasoline with the hydrogenated light cracked gasoline and theheavy cracked gasoline, respectively, to form a `blended aviation fueloi' low acid heat and high antiknock. f

2. The method of claim 1 which includes the further step of separatingbutanes, pentanes and lighter hydrocarbons from the naphtha fractionprior to dehydro-aromatization, removing lighter hydrocarbons from saidseparated butanes and pentanes and blending said butanes and pentaneswith the aromatic gasoline fraction, hydrogenated light cracked gasolinefraction and heavy cracked gasoline fraction, respectively, to form anaviation fuel of improved volatility, knock rating and lead response.

3. The method of claim 1 which includes the step by hydrogenating atleast a part of the light aromatic gasoline simultaneously with thehydrogenation of the catalytically cracked gasoline.

4. The method of making high quality gasoline from a charging stockcontaining naphtha and gas oil which method comprises catalyticallydehydro-aromatizing said naphtha to produce hydrogen, aromatic gasolineand an aromatic oil heavier than gasoline, catalytically cracking saidgas oil in the presence of said aromatic oil heavier-than-gasoline,separating the catalytic cracking products into a light gasolinefraction and a hydrogenating said light cracked gasoline fraction toeffect saturation oi' at least but' not more than 90% of the olenscontained therein vwith hydrogen produced in the dehydro-aromatizationstep and blending the hydrogenated product with the aromatic gasolineand the heavy cracked gasoline fractions, respectively. t

5. The method of lowering the acid heat of catalytically crackedgasoline without unduly impairing its octane number and tetraethyl leadresponse, ,which method comprises fractionating `said cracked gasolineinto a, light fraction having an end point of 150 to 250 F. and a heavyfraction, respectively, hydrogenating said light fractionto eieot atleastA 20% saturation but not more than 90% saturation of the-olenscontained therein and blending the partially hydrogenated lightyfraction with the unhydrogenated heavy fraction.

6. The method of lowering lytically cracked gasoline .without undulyimpairing its octane number and tetraethyl lead response, which methodcomprises partially hydrogenating a light fraction of saidvcatalytically cracked gasoline having an end point of 150 to 250 F. toeffect about 60% to 75% saturation of acid heat of catal the olefinscontained therein and blending the partially hydrogenated light fractionwith an unhydrogenated heavy fraction of said catalytically crackedgasoline. 7. An integrated process for making low acid heat, high octanenumber gasoline from petroleurn charging stocks containing hydrocarbonsof the naphtha and gas oil boiling ranges, which method comprisesdehydro-aromatizing a naphtha fraction of the charging stock for theproduction of an aromatic gasoline .fraction 'catalytically cracking agas oil 'fraction of said charging stock, fractionating the products ofthe cata,- lytic cracking step to obtain a light naphtha fraction havingan end point of about 150 to 250 F., partially hydrogenating said lightnwphtha fraction to saturate at least 20% butnot more than 90% of theoleiins contained therein anda mended aviation fuei of1ow acid heat andhigh i antiknock.

'8. An integrated process for making low acid v heat,` high octanenumber gasoline from charging stocks containing n'aphtha and gas oil,which method comprises dehydro-aromatizing a naphtha fraction of saidcharging stock to produce hydrogen, a gasoline fraction and a fractionheavier than gasoline, catalytically cracking the fraction heavier thangasoline with a gas oil fraction from the charging stock, separating thecatalytically cracked products into a light cracked gasoline fractionhaving an end point of 150 to 250 F. and a heavier fraction,hydrogenating the light cracked gasoline fraction to an extentsufficient to saturate yat least 20% but not more than 80% of theoleiins contained therein, effecting said hydrogenation with hydrogenproduced in the dehydro-aromatization step and blending the hydrogenatedcracked fraction with the gasoline produced by dehydro-aromatization toform a blended motor fuel of low acid heat and high antiknockproperties. i

9. The method of claim 8 wherein the hydrogenation is effected underconditions for obtaining saturation of at least 60% but not more than'15% of the oleiins in the catalytically cracked gasoline fraction.

10. A' hydrocarbon conversion process which.

comprises catalytically dehydro-aromatizlng A naphtha to producehydrogen, a gasoline fraction and a fraction heavier than gasoline,catalytically cracking the heavier-than-gasoline fraction, sep- -aratinga cracked gasoline having an end `point of to 250 F. from the productsof the catalytic cracking step and partially hydrogenating the ROBERTF.. MARSCI-INER.

